• Journal of Powder Materials
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• v.24 no.2
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• pp.122-127
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• 2017

Fe-6.5 wt.% Si alloys are widely known to have excellent soft magnetic properties such as high magnetic flux density, low coercivity, and low core loss at high frequency. In this work, disc-shaped preforms are prepared by spark plasma sintering at 1223 K after inert gas atomization of Fe-6.5 wt.% Si powders. Fe-6.5 wt.% Si sheets are rolled by a powder hot-rolling process without cracking, and their microstructure and soft magnetic properties are investigated. The microstructure and magnetic properties (saturation magnetization and core loss) of the hot-rolled Fe-6.5 wt.% Si sheets are examined by scanning electron microscopy, electron backscatter diffraction, vibration sample magnetometry, and AC B-H analysis. The Fe-6.5 wt.% Si sheet rolled at a total reduction ratio of 80% exhibits good soft magnetic properties such as a saturation magnetization of 1.74 T and core loss ($W_{5/1000}$) of 30.7 W/kg. This result is caused by an increase in the electrical resistivity resulting from an increased particle boundary density and the oxide layers between the primary particle boundaries.

• Current Optics and Photonics
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• v.1 no.4
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• pp.402-411
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• 2017

Combined LIBS-Raman spectroscopy has been widely studied, due to its complementary capabilities as an elemental analyzer that can acquire signals of atoms, ions, and molecules. In this study, the classification of polymorphs was performed by laser-induced breakdown spectroscopy (LIBS) to overcome the limitation in molecular analysis; the results were verified by Raman spectroscopy. LIBS signals of the $CaCO_3$ polymorphs calcite and aragonite, and $CaSO_4{\cdot}2H_2O$ (gypsum) and $CaSO_4$ (anhydrite), were acquired using a Nd:YAG laser (532 nm, 6 ns). While the molecular study was performed using Raman spectroscopy, LIBS could also provide sufficient key data for classifying samples containing different molecular densities and structures, using the peculiar signal ratio of $5s{\rightarrow}4p$ for the orbital transition of two polymorphs that contain Ca. The basic principle was analyzed by electronic motion in plasma and electronic transition in atoms or ions. The key factors for the classification of polymorphs were the different electron quantities in the unit-cell volume of each sample, and the selection rule in electric-dipole transitions. The present work has extended the capabilities of LIBS in molecular analysis, as well as in atomic and ionic analysis.

• Korean Journal of Microbiology
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• v.30 no.5
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• pp.333-338
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• 1992

Saccharomyces cerevisiae contains 10-nm tilament ring which lies just under the inner surface of the plasma membrane within the mother-bud neck. Although H)-nm filaments may he involved in cellular morphogenesis. their role and organization are not clear. Here we report the production of antihodies specific for the CDel2 protein hy use of gene fusion techniques. and studies on the organization and function of IO-nm filaments using these antibodies. The CDCl2 protein arc translated through the whtlle cell cycle and present in the cytosol. 'They are polymerized just before bud emergence and unpolymerized alier cytokinesis. and do not have organizational relationship with actin. Thc possible role of 10-nm filaments is the determination of bud emergence site and completion of cytokinesis.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2002.11a
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• pp.14-19
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• 2002

In this study, as Cu diffusion barrier, tantalum nitrides were successfully deposited on Si(100) substrate and SiO2 by plasma assisted atomic layer deposition(PAALD) and thermal ALD, using pentakis (ethylmethlyamino) tantalum (PEMAT) and $NH_3$ as precursors. The TaN films were deposited on $250^{\circ}$C by both method. The growth rates of TaN films were $0.8{\AA}$/cycle for PAALD and $0.75{\AA}$/cycle for thermal ALD. TaN films by PAALD showed good surface morphology and excellent step coverage for the trench with an aspect ratio of h/w - $1.8 : 0.12 \mu\textrm{m}$ but TaN films by thermal ALD showed bad step coverage for the same trench. The density for PAALD TaN was $11g/\textrm{cm}^3$ and one for thermal ALD TaN was $8.3g/\textrm{cm}^3$. TaN films had 3 atomic % carbon impurity and 4 atomic % oxygen impurity for PAALD and 12 atomic % carbon impurity and 9 atomic % oxygen impurity for thermal ALD. The barrier failure for Cu(200nm)/TaN(l0nm)/$SiO_2(85nm)$/Si structure was shown at temperature above $700^{\circ}$C by XRD, Cu etch pit analysis.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.11a
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• pp.105-108
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• 2002

환경에 관한 관심이 증대되면서 Sn37Pb 솔더를 대체하기 위한 새로운 무연솔더의 개발이 진행되고 있다1). 또한 연구의 초점이 되고 있는 것이 플럭스의 사용에 관한 것이다. 플럭스는 솔더의 산화막을 제거하는데 필수적이지만, 플럭스 세정제의 독성 문제로 무플럭스 솔더링에 대한 관심이 크게 증대되고 있다2),3). 무플럭스 솔더링의 방법에는 여러 가지가 있으며, 그 중 한가지가 플라즈마를 이용한 방법이다4). 본 연구에서는 솔더표면의 이물질과 산화막을 제거하기 위한 플라즈마 처리가 접합 후, 접합부에 미치는 영향에 대해서 알아보았다. 기판은 Evaporator를 이용하여 Au/Cu/Ni/Al UBM을 증착한 Si-wafer를 사용하였다. 사용된 솔더는 Sn37Pb, Sn3.5Ag와 Sn3.5Ag0.7Cu 솔더볼이며, 열중 및 적외선 겸용 리플로 머신과 Ar＋H$_2$를 이용한 플라즈마 에쳐를 사용하여 범프를 형성하였다. 플라즈마 처리가 계면의 미세조직과 기계적 강도에 끼치는 영향을 알아보기 위하여 플라즈마 처리된 시편과 리플로 한 후의 시편을 비교 분석하였다. 전단시험기로 계면의 강도를 측정하였으며, 주사전자현미경으로 범프의 표면과 계면 및 전단파면을 관찰하고 이에 대하여 고찰하였다. 산화막제거를 위한 플라즈마 처리가 저음점인 솔더의 미세조직을 기존의 솔더링 접합부와는 다르게 변화시킴으로써 솔더부의 전체적인 특성에 영향을 끼치는 것을 알 수 있었다.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.6
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• pp.656-662
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• 2015

In the present study, multi-layered Si DLC (Silicon Diamond-Like Carbon) coatings with HMDSO (Hexamethyldisiloxane) buffer layers are applied on SKD 11 substrates by PECVD (Plasma Enhanced Chemical Vapor Deposition) with different HMDSO gas flow rates, while the gas flow rate of $C_2H_2$ is fixed to enhance the electric resistivity of forming dies for electrically assisted forming. The HMDSO buffer layer is introduced to increase adhesion between the base metal and Si-DLC layers. The result of evaluation of electric resistivity and adhesion strength shows that the properties are affected by the flow rate of HMDSO, while the flow rate of 80 sccm results in the coating with the highest electric resistivity and adhesion strength among the selected flow rates.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.323-323
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• 2010

Saw damage of crystalline silicon wafer is unavoidable factor. Usually, alkali treatment for removing the damage has been carried out as the saw damage removal (SDR) process for priming the alkali texture. It usually takes lots of time and energy to remove the sawed damages for solar grade crystalline silicon wafers We implemented two different mixed acidic solution treatments to obtain the improved surface structure of silicon wafer without much sacrifice of the silicon wafer thickness. At the first step, the silicon wafer was dipped into the mixed acidic solution of $HF:HNO_3$=1:2 ration for polished surface and at the second step, it was dipped into the diluted mixed acidic solution of $HF:HNO_3:H_2O$=7:3:10 ratio for porous structure. This double treatment to the silicon wafer brought lower reflectance (25% to 6%) and longer carrier lifetime ($0.15\;{\mu}s$ to $0.39\;{\mu}s$) comparing to the bare poly-crystalline silicon wafer. With optimizing the concentration ratio and the dilution ratio, we can not only effectively substitute the time consuming process of SDR to some extent but also skip plasma enhanced chemical vapor deposition (PECVD) process. Moreover, to conduct alkali texture for pyramidal structure on silicon wafer surface, we can use only nitric acid rich solution of the mixed acidic solution treatment instead of implementing SDR.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.200.1-200.1
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• 2013

실리콘 태양전지 표면에는 구조적인 결함에 의해 소수 캐리어의 재결합이 일어난다. 재결합에 의해 캐리어의 반송자 수명은 줄어들게 되고, 태양전지의 효율은 감소하게 된다. 이를 줄이기 위해 태양전지 전 후면에 패시베이션을 하게 되는데, 이번 연구는 단결정 실리콘 태양전지 전면에 SiNx막을 증착함으로 수소 패시베이션이 반송자 수명에 미치는 영향에 대하여 연구하였다. 공정을 위해 $156{\times}156mm^2$, 200 ${\mu}m$, 0.5-3.0 ${\Omega}{\cdot}cm$ and p-type 단결정 실리콘 웨이퍼를 사용하였고, SiNx막을 올리기 전에 KOH 8.5% 용액으로 SDR을 실행하였다. RF-PECVD 장비로 SiNx 막을 증착하였고 증착 온도는 $200{\sim}400^{\circ}C$, 반응기 내부의 압력을 200~1,000 mtorr, SiH4/NH3/N2 각각의 가스 비율 조절, 그리고 플라즈마 RF power 변화시킴에 따라 증착된 SiNx막의 균일도 및 특성을 분석하였다. 반사광 측정 장비인 Reflectometer장비로 막의 두께와 굴절률, 반사율을 측정하였고, 반송자 수명을 측정하여 태양전지의 표면결함을 최대한 패시베이션 시켜주는 조건에 대한 연구를 수행하였다.

• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.740-747
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• 2009

The purpose of this study is to identify the effect of electrolyte compositions on electrodeposited copper foil. First of all, the polyimide substrate was pretreated with plasma. Finally, copper foil was deposited on a Cu/Ni/Polyimide substrate using the electroplating technique. As the quantity of Cu increased, preferred orientations changed into (111). Increasing sulfuric acid, on the other hand, brought down the preferred orientation of (111). The lowest sheet resistance, surface roughness, and fine adhesion were detected when the ratio of $Cu^{2+}$ and $H_2SO_4$ is 50:50(g/l).

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.44-44
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• 2003

Growth mechanism of carbon nanotubes(CNTs) synthesized by chemical vapor deposition is abided by two growth modes. These growth modes are classified by the position of activated catalytic metal particle in the CNTs. Growth mode can be also affected by interaction between substrate and catalytic metal and induced energy such as thermal and plasma. We studied the reaction of catalytic metal to the substrate and growth mode of CNTs. Various substrates such as Si(100), graphite plate, coming glass, sapphire and AAO membrane are used to study the relation between catalytic metal and substrate in the synthesis of CNTs. For catalytic metal, thin film was deposited on various substrate via sputtering technique with a thickness of ∼20nm and magnetic fluids with none-sized particles were dispersed on AAO membrane. After laying process on AAO membrane, it was dried at 80$^{\circ}C$ for 8 hour. Synthesizing of CNTs was carried out at 900$^{\circ}C$ in NH3/C2H2 mixture gases flow for 10minutes.